Entamœba phagocytoides (Gauducheau, 1908). This parasite was discovered in a case of dysentery at Hanoi, Indo-China. The amœba is small, 2 µ to 15 µ in diameter. It is active. It ingests bacteria and red blood corpuscles, while peculiar spirilla-like bodies are found in its cytoplasm. It multiplies by binary and multiple fission. It can be cultivated. More recently (1912) the author appears to consider the amœba to be a stage of a Trichomonas, but abandons the view later (1914). Further researches on this organism are needed.
Entamœba minuta (Elmassian, 1909)[28] was found, in association with E. coli, in a case of chronic dysentery in Paraguay. It resembles E. tetragena but is smaller, rarely exceeding 14 µ in diameter. Schizogony occurs, four merozoites being produced. The encystment is total and endogenous, giving rise to cysts containing four nuclei. This amœba is considered by Darling and others to be the pre-cyst trophozoite stage of E. histolytica (tetragena).
Entamœba nipponica (Koidzumi, 1909) was found in the motions of Japanese suffering from dysentery or from diarrhœa, in the former case in company with Entamœba histolytica. Its diameter is 15 µ to 30 µ. The endoplasm is phagocytic for red blood corpuscles. The nucleus is well defined, resembling that of E. coli and of E. tetragena. Multiplication occurs by binary fission and by schizogony. Encystment is total, but has not been completely followed. Darling and others consider that this is an abnormal form of E. histolytica, while Akashi (1913) doubts if it is an amœba at all, but rather is to be regarded as shed epithelial cells.
General Remark.—It is now considered by some workers that true Entamœbæ cannot be cultivated on artificial media. Quite recently Williams and Calkins (1913)[29] have somewhat doubted this opinion, and state that certain cultural amœbæ, originally obtained from Musgrave in Manila, exhibit the various morphological variations associated with true entamœbæ of the human digestive tract.
Entamœba buccalis, Prowazek, 1904.
The size varies from 6 µ to 32 µ. Ectoplasm is always present; the endoplasm contains numerous food-vacuoles. The nucleus is vesicular, with a greenish tinted membrane which is poor in chromatin. The size of the nucleus is from 1·5 µ to 4·5 µ. A contractile vacuole is not visible. The pseudopodium is broad. It was discovered in the mouths of persons with dental caries at Rovigno and also at Trieste, being most easily found in dense masses of leucocytes, also among leptothrix and spirochæte clusters. It can be easily distinguished from leucocytes by more intense staining with neutral red. Multiplication proceeds by fission. Transmission may take place through the small spherical cysts. This species (fig. 10) has since been observed in Berlin, and is also occasionally found in carcinoma of various regions of the oral cavity. (Leyden and Löwenthal, 1905).
Fig. 10.—Entamœba buccalis, Prow. a-d, the same specimen observed during five minutes. × 1,000. e, amœba fixed and stained with iron-hæmatoxylin. × 1,500. (After Leyden and Löwenthal.)